I met a young woman recently who swears by psilocybin as the only thing which controls her cluster headaches....and she claims to take much less than a psychedelic dose, something in the .5-1g range every few weeks.
dude i actually saw something on nat geo or one of those channels about an older gentleman uses them for the same reason. he's not the druggie type but uses the mushrooms because he swears they are the only preventative measure he can take to stop the cluster headaches. he doesn't like to do it every month or couple month i forget but his family supports it because he needs it. he just grounds them up into capsules takes a few and lays around while he's on them and waits for it to wear off. apparently he's good to go afterward.